#include <tommath.h>
#ifdef BN_MP_DIV_2D_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
 */

/* shift right by a certain bit count (store quotient in c, optional remainder in d) */
int mp_div_2d(mp_int * a, int b, mp_int * c, mp_int * d)
{
	mp_digit D, r, rr;
	int x, res;
	mp_int t;

	/* if the shift count is <= 0 then we do no work */
	if (b <= 0) {
		res = mp_copy(a, c);
		if (d != NULL) {
			mp_zero(d);
		}
		return res;
	}

	if ((res = mp_init(&t)) != MP_OKAY) {
		return res;
	}

	/* get the remainder */
	if (d != NULL) {
		if ((res = mp_mod_2d(a, b, &t)) != MP_OKAY) {
			mp_clear(&t);
			return res;
		}
	}

	/* copy */
	if ((res = mp_copy(a, c)) != MP_OKAY) {
		mp_clear(&t);
		return res;
	}

	/* shift by as many digits in the bit count */
	if (b >= (int)DIGIT_BIT) {
		mp_rshd(c, b / DIGIT_BIT);
	}

	/* shift any bit count < DIGIT_BIT */
	D = (mp_digit) (b % DIGIT_BIT);
	if (D != 0) {
		register mp_digit *tmpc, mask, shift;

		/* mask */
		mask = (((mp_digit) 1) << D) - 1;

		/* shift for lsb */
		shift = DIGIT_BIT - D;

		/* alias */
		tmpc = c->dp + (c->used - 1);

		/* carry */
		r = 0;
		for (x = c->used - 1; x >= 0; x--) {
			/* get the lower  bits of this word in a temp */
			rr = *tmpc & mask;

			/* shift the current word and mix in the carry bits from the previous word */
			*tmpc = (*tmpc >> D) | (r << shift);
			--tmpc;

			/* set the carry to the carry bits of the current word found above */
			r = rr;
		}
	}
	mp_clamp(c);
	if (d != NULL) {
		mp_exch(&t, d);
	}
	mp_clear(&t);
	return MP_OKAY;
}
#endif

/* $Source: /cvs/libtom/libtommath/bn_mp_div_2d.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */